Among the greatest benefits which accrue to a civilized society are those which cause garbage and sewage wastes to "disappear". Although a city resident might generate only 3.5 lb of garbage waste and 1.5 lb. of sewage waste per day, even a small city of 250,000 population will have to dispose of 875,000 pounds of garbage and 375,000 pounds of sewage waste each day. Our political system has provided huge infrastructures to collect and dispose of this waste. Most garbage waste is deposited in landfills. Typically a landfill owner charges from fifty to one hundred dollars per ton for accepting garbage. At the $50.00 rate the above municipality has to budget $8,000,000.00 annually just to pay these "tipping" fees. The costs of collection and transport are extra.
To make matters worse, local landfills are filling up, mandating that garbage be transported further from its source. Our highways become clogged with huge trucks performing this odorous task.
In an effective attempt to address and minimize this problem, municipalities have established trash to energy plants which burn the garbage producing heat, use the heat to generate steam and the steam to generate electricity. The electricity is in turn sold to the local utility or sold to a local bulk electricity consumer.
The burning process reduces the mass of material to be disposed of by 85 to 90 percent, thereby reducing tipping costs and also extending the life of local landfills. However, the trash burning plant must first cool the fiery ash by soaking it with water which it must buy from the local water company and then pay a hauler to cart away the, now much heavier, wet ash. Water has become a scarce resource. Persistent droughts and high rates of usage have lowered water levels in lakes and rivers. Threats of water shortage abound.
Haulers in the past have always transported the cooled wet ash to the landfill and paid to tip it.
In other places, huge quantities of earth which have been contaminated by oil or in other ways are being incinerated to vaporize the contaminant oils. The hot earth must then be cooled and disposed of, just like the hot ash from the trash to steam plant or from coal burning power plants.
To address the sewage problem municipalities have invested in sewage disposal plants. Here settling tanks, water treatment and disinfectant facilities have been provided to separate the water from the solids and treat, purify and dispose of the water in rivers or streams. Even though the solids are squeezed to press out much of the water, the average water content of the pressed solids is 75 to 85 percent. In some locations the wet solids are heated by fuel burning furnaces to dry and disinfect them, and again disposed of in landfills. Fuel costs to achieve this drying and sterilization function by evaporating the residual water are high. This is because while it take considerable amounts of heat to heat water to the boiling point, it takes 7.5 times as much heat to evaporate the hot water as to heat it to the boiling point. Even without evaporating much of the water the fuel costs for heating the wet solids is very high because it takes roughly five times as much heat to raise the water component of the wet solids to a temperature of 190.degree. F., the temperature required for effective sterilization, as it would have taken to heat the solids to that temperature if they had been dry.